From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756528AbdLOUbd (ORCPT ); Fri, 15 Dec 2017 15:31:33 -0500 Received: from mga14.intel.com ([192.55.52.115]:63336 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756401AbdLOUb2 (ORCPT ); Fri, 15 Dec 2017 15:31:28 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.45,406,1508828400"; d="scan'208";a="12671404" From: Jarkko Sakkinen To: intel-sgx-kernel-dev@lists.01.org, platform-driver-x86@vger.kernel.org, x86@kernel.org Cc: linux-kernel@vger.kernel.org, Jarkko Sakkinen , Jonathan Corbet , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , linux-doc@vger.kernel.org (open list:DOCUMENTATION) Subject: [PATCH v8 6/8] intel_sgx: driver documentation Date: Fri, 15 Dec 2017 22:27:24 +0200 Message-Id: <20171215202936.28226-7-jarkko.sakkinen@linux.intel.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20171215202936.28226-1-jarkko.sakkinen@linux.intel.com> References: <20171215202936.28226-1-jarkko.sakkinen@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=y Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Signed-off-by: Jarkko Sakkinen Tested-by: Serge Ayoun --- Documentation/index.rst | 1 + Documentation/x86/intel_sgx.rst | 101 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 102 insertions(+) create mode 100644 Documentation/x86/intel_sgx.rst diff --git a/Documentation/index.rst b/Documentation/index.rst index cb7f1ba5b3b1..ccfebc260e04 100644 --- a/Documentation/index.rst +++ b/Documentation/index.rst @@ -86,6 +86,7 @@ implementation. :maxdepth: 2 sh/index + x86/index Korean translations ------------------- diff --git a/Documentation/x86/intel_sgx.rst b/Documentation/x86/intel_sgx.rst new file mode 100644 index 000000000000..59049a35512f --- /dev/null +++ b/Documentation/x86/intel_sgx.rst @@ -0,0 +1,101 @@ +=================== +Intel(R) SGX driver +=================== + +Introduction +============ + +Intel(R) SGX is a set of CPU instructions that can be used by applications to +set aside private regions of code and data. The code outside the enclave is +disallowed to access the memory inside the enclave by the CPU access control. +In a way you can think that SGX provides inverted sandbox. It protects the +application from a malicious host. + +There is a new hardware unit in the processor called Memory Encryption Engine +(MEE) starting from the Skylake microarchitecture. BIOS can define one or many +MEE regions that can hold enclave data by configuring them with PRMRR registers. + +The MEE automatically encrypts the data leaving the processor package to the MEE +regions. The data is encrypted using a random key whose life-time is exactly one +power cycle. + +You can tell if your CPU supports SGX by looking into ``/proc/cpuinfo``: + + ``cat /proc/cpuinfo | grep sgx`` + +Enclave data types +================== + +SGX defines new data types to maintain information about the enclaves and their +security properties. + +The following data structures exist in MEE regions: + +* **Enclave Page Cache (EPC):** memory pages for protected code and data +* **Enclave Page Cache Map (EPCM):** meta-data for each EPC page + +The Enclave Page Cache holds following types of pages: + +* **SGX Enclave Control Structure (SECS)**: meta-data defining the global + properties of an enclave such as range of addresses it can access. +* **Regular (REG):** containing code and data for the enclave. +* **Thread Control Structure (TCS):** defines an entry point for a hardware + thread to enter into the enclave. The enclave can only be entered through + these entry points. +* **Version Array (VA)**: an EPC page receives a unique 8 byte version number + when it is swapped, which is then stored into a VA page. A VA page can hold up + to 512 version numbers. + +Launch control +============== + +For launching an enclave, two structures must be provided for ENCLS(EINIT): + +1. **SIGSTRUCT:** a signed measurement of the enclave binary. +2. **EINITTOKEN:** the measurement, the public key of the signer and various + enclave attributes. This structure contains a MAC of its contents using + hardware derived symmetric key called *launch key*. + +The hardware platform contains a root key pair for signing the SIGTRUCT +for a *launch enclave* that is able to acquire the *launch key* for +creating EINITTOKEN's for other enclaves. For the launch enclave +EINITTOKEN is not needed because it is signed with the private root key. + +There are two feature control bits associate with launch control: + +* **IA32_FEATURE_CONTROL[0]**: locks down the feature control register +* **IA32_FEATURE_CONTROL[17]**: allow runtime reconfiguration of + IA32_SGXLEPUBKEYHASHn MSRs that define MRSIGNER hash for the launch + enclave. Essentially they define a signing key that does not require + EINITTOKEN to be let run. + +The BIOS can configure IA32_SGXLEPUBKEYHASHn MSRs before feature control +register is locked. + +It could be tempting to implement launch control by writing the MSRs +every time when an enclave is launched. This does not scale because for +generic case because BIOS might lock down the MSRs before handover to +the OS. + +Debug enclaves +-------------- + +Enclave can be set as a *debug enclave* of which memory can be read or written +by using the ENCLS(EDBGRD) and ENCLS(EDBGWR) opcodes. The Intel provided launch +enclave provides them always a valid EINITTOKEN and therefore they are a low +hanging fruit way to try out SGX. + +SGX uapi +======== + +.. kernel-doc:: drivers/platform/x86/intel_sgx_ioctl.c + :functions: sgx_ioc_enclave_create + sgx_ioc_enclave_add_page + sgx_ioc_enclave_init + +.. kernel-doc:: arch/x86/include/uapi/asm/sgx.h + +References +========== + +* System Programming Manual: 39.1.4 Intel® SGX Launch Control Configuration -- 2.14.1